The first 10 days of Dhu-l-Hijjah are the best ten days of the year. Dhu-l-Hijjah starts on Sunday 12th August 2018. The Day of Arafah will be Monday 20th August and Eid will be Tueday 21st August 2018.

The Prophet (peace and blessings of Allaah be upon him) said: “There are no days on which righteous deeds are more beloved to Allaah than these ten days.”

From Anas (may Allaah be pleased with him) that the Prophet (peace and blessings of Allaah be upon him) said: “There is no deed that is better before Allaah or more greatly rewarded than a good deed done in the (first) ten days of al-Adha.”

These texts and others indicate that these ten days are better than all other days of the year, with no exception, even the last ten days of Ramadaan. But the last ten nights of Ramadaan are better than the first ten nights of Dhu’l-Hijjah, because they include Laylat al-Qadr, which is better than a thousand months.

Making the Sacrifice (Udhhiya or Qurbani) is strongly recommended for the head of each household. The one who intends to do so should refrain from cutting their nails or hair during these ten days until after the eid prayer and when then sacrifice has been made.

Fasting the Day of Arafah - the 9th of Dhul-Hijjah - is an expiation for the minor sins of the previous year and for the following year, so every effort should be made to fast this day.

See http://www.islam-qa.com/en/49042